Railway signaling



Nov. 8, 1927.

L. O. GRONDAHL RAILWAY siGNALmG 9, 1921 2 Sheets-Steet 1 Original Filed Dec.

A .0. Gm i A Nov. 8, 1927.

- ReL, 5 8.4 L. O. GRONDAHL RAILWAY SIGNALING v I I I Original Filed Dec. 9, 1921 2 Sheets-Sheet 5 fiv l E INVENTORZ A,.0.Gron

Reiaued Nov. 8, 1927.

a 1 UNITED STATES Re. 16,784 PATENT 'oFFi E- I LABS O. GRONDAHL, OI PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

RAILWAY SIGNALING.

Original application filed December 9, 1921, Serial No. 521,147. Renewed August 2,1926. Original No. 1,619,928, dated March 8, 1927. Application for reissue filed July 21, 1927. Serial No. 207,551. I

My invention relates to railway signaling, andis particularly well adapted to slgnallng of the type wherein roadside slgnals are governed by track circuits which in turn are controlled by the passage of cars or tram along the track. 0 a

I will describe several forms of signaling apparatus embodying my invention, and w ll then pointout the novel features thereof in claims. j 7

In the accompanying drawings, Flg. 1 1s a diagrammatic view showing one form of apparatus embodying my inven t1on. Figs.

, 2 and 3 are Views showing modifications of the apparatus shown in Fig. 1.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Fig. 1, the reference characters F and F designate the track rails of a railway along which trafiic normally'moves in the direction indicated by the arrow. These rails are divided into a plurality of successive track sections AB, B C, .CD, etc., the isolation of the track sections being accomplished, as here shown,

by insulated'joints 2 in both of the lines of rails. Any other suitable method of isolating the sections may be employed,'however, without departing from the sp rit and scope of my invention.

Located adjacent the entrance end of each track section is a signal designated by the reference character S, with an exponent corresponding to the location. Each slgnal, as here shown, comprises three lamps G, Y and R, which, when lighted, indicate proceed, caution and stop, respectively.

, ,Each track section is provided with a track circuit comprising a source of current and a relay. As here shown, the source of current for each track circuit is the secondary' 3 of a transformer designated by the reference character T with an exponentcorresponding to the location, the primary 22 0f which is connected with a transmission line 5. to which alternating current is constantly supplied by a generator 4. The relay for each track' circuit is designated K and is of the thermo-sensitive type comprising a heating element 6: and thermosensitive element 7, the heating element being connected across the rails adjacent the entrance end of the section. The thermosensitive relay K hasa negative temperature coeflicient, that is, the resistance of the element 7 decreases with increase of tem 'erature, and so with increase of current owing in the heating element 6.

Referring specifically. to signal S, the proceed lamp Gris provided with a circuitwhich passes from the left hand terminal of secondary 8 of transformer T through a ballast resistance 9, wireulO, heating element of a thermo-sensitive relay K wire 11, lamp G, wire'12, thermo-sensitive element of the relay K and wire 13 to the right-hand terminal of secondary 8. Connected across the secondary 8 and in shunt with the other elements of the circuit just traced are the heating elements of two thermo-sensitive relays K and K; Each relay K, K and K? has a negative temperature coefficient. The parts of this circuit are so adjusted that when relay K is energized, that is, when track section AB is unoccupied, sufiicient current flows through lamp G to light this lamp and the current in the heating element of relay K is sufficient to energize this relay. The drop in voltage across the several elements in the circuit is then such that relays K and Kf ar'e de-e'nergized; When sect-ion AB' is occupied by a car or train, however, relay K is de -energized and the current which then flows through lamp G'is insufiicient to light this lamp. The voltage drop across lamp G and relays K and K is then such that relays K and K become energized.

The stop lamp R for signal S is provided with a circuit which includes a secondary 14 I of transformer T and the thermo-sensitive element of relay K The parts of this circuit are so adjusted that when relay K is de-energized, lamp R is extinguished, but that when relay K becomes energized, such as when section A-B is occupied by a car or train, the amount of current which flows in the circuit is sufiic'ient to light the stop lamp R.

The caution lamp Y for signal S is provided with a circuit which passes from the left-hand terminal of secondary 15 of transformer T through wire 16, thermo-sensitive element of relay K a't location A, wires 13, 17 and 11, thermo-sensitive element of relay K, primary of transformer 19, wire 20, lamp Y, and wire 21 to secondary 15 of-transformer T The partsof this circuit are so I adjusted that when "relays "K and K are both energized, the current which flows in lamp Y is sufiicient to light this lamp, but that when either of the said relaysbecomes tie-energized, the current is reduced to such value that lamp Y is extinguished.

The secondary of transformer 19 is con nected with the heating element 01 a thermosensitive relay K having anegative tem-' perature coefficient and the thermo-sensitive element of which is connected across the terminals of the proceed lamp G. The purpose of this transformer and relay is to suppress or extinguish lamp G when the caution lamp Y oft-he same signal is burning; To do this, the parts are so adjusted that when lighting current is supplied to lamp 'Y, the

secondary of transformer 19 delivers sufficient current to energize relay K so that a shunt of low resistance is provided around lamp G. \Vhen lamp Y is extinguished, however, the current in transformer 19 is not of sufficient value to energize relay K and so the shunt around lamp G has a comparatively high resistance, and thisshunt' lay K at location A is energized, however,

so that stop lamp R is lighted. At location B the stop lamp R is extinguished because the associated relay K is deenergized." The caution lamp Y is lighted, however,,because relay K at signal S and relay K at signal S are both energized. The proceed lamp G of signal S is extinguished because the ad jacent relay K is energized. At signal S the stop lamp R is extinguished because the adjacent relay K is de-energi zed, and the caution lamp Y is extinguished becausere- 'lay K at location'B is de-energized. The

proceed lamp G is lighted, however, because the adjacent track relay K is energized.

Referring now to Fig. 2, the track circuits are the same as in Fig. 1, but the con trol of the signals by these track circuits is somewhat diiferent. Considering location B, for example, the track relay K controls a circuit which passes from the left-hand terminal of secondary 8 of transformer T through resistance 9, heating element of a relay K thermo-sensitive; element of relay K heating element of a relay K and wires 22 and 23 to the secondary 8 of transformer T The stop lamp R is connected in this circuit in shunt around relays K K and K so that this lamp is connected withsecondary 8, but with a resistance 9 interposed between the secondary and the lamp The parts of the circuit are so adjusted that when relay K is energized,

relays -K and K are also energized and the voltage across lamp R is insufficient to light this lamp ,but that when relay K is deenergized, due, for example, to the presence or a car ortraln 1n sectlon AB, relays K and K also become de energized and the voltage which is then applied to lamp R is tl-iern'io-se-nsitive element of relay K at 10-- cation A, wire 31, lamp G, wire 30, thermosensitive element of relay K at location B,

and wires 26 and 25 to secondary 24 of transformer T The parts of this circuit are so ad usted that lamp G'is lighted only when relay K? at location A and relay K? at location Bare both energized.

- The caution lamp Y at location B is pro vided witha circuit which passes from secondary 24 of transformer T through resistance 29, wire 28, lamp Y, wire 27 thermosensitlve element of relay K and wires 26 and 25 to secondary 24L of transformer'T The parts of this circuit are so adjusted that lamp Y is lighted when the adjacent relay K is energized provided that lamp G of the same signal is extinguished. To'accomplish thisoperation of lamps G and Y, lamp G is preferably a low voltage lamp, such as 6 volts, while lamp Y is a high voltage lamp, sucha's 110 volts. The resistance 29 being in series with both lamps, it is then obvious that lamp and thermo-sensitive relay 'K constitute a. shunt of low resistance around lamp Y, so that when lamp G is illuminated lamp Y will be extinguished;

As shown inthe drawing, the track section to the left of location A is occupied by a car ortrain so that track relay K at location A isde energized. Itfollows that lamp R of signal S is lighted because of the high resistance of the thermo-sensitive element of relay K and so signal S indicates stop. As for signal S the stop lamp R is extinguished because the adjacent relay K is energized, and the proceed lamp G is extinguished because relay K at location A is tie-energized. 'The ,caution lamp Y is lighted, however, because't-he adjacent relay K is energized. In signal S the stop lamp R'is extinguished because the adjacent relay K is energized, and the proceed lamp G is lighted because the adjacent relay K and the relay K at location B are both energizech The caution lamp Y is extinguished because this lamp is shunted by lamp G of the same signal and relay K at location B.

Referring now to Fig. 3, the track circuit is again the same as in Fig. 1, but the control of the' signal lamps by the track relays is accomplished with a still different arrangement of circuits and apparatus. In this view each track relay K controls a circuit which includes the secondary 8 of the provided with a shunt or branch circuit which includes the thermo-sensitive element of the adjacent relay K.

The parts of this circuit are so adjusted that lamp R will be extinguished when relay K is energized, and lighted when relay K is de-energized; that is, when relay K is energized the resistance of the tllGIIDO-SQIISI- tive element of this relay is so low that suiiicient current is diverted from lamp R to extinguish the lamp, or to express the matter in another way, the voltage across this lamp is then insuflicient to light the lamp. i The proceed lamp G'of signal S is provided with acircuit which passes from secondary 33 of transformer T through wires 34 and 34, lamp G, wire 35, thermo-sensitive element of. relay K at location B, wires 36 an d 37, t-hermo-sensitive elementof relay K at location A, and wire 38 to secondary 33 of transformer T. The parts of this circuit are so adjusted that lamp G islighted when both relays K and K are energized, but

extinguished when either of these relays is de-energized.

The caution lamp Y of signal S is included in a circuit which passes from secondary 15 of transformer T through wire' 41*, lamp Y, wire 41, primary of transformer 42, wire 40, heating element of relay K, wire 35, thermo-sensitive element of relay K and wire 39 to secondary 15. This circuit is so adjusted that lamp Y is lighted when relay K is energized, provided that the secondary of'transformer L2 is not supplied with current by induction from the primary of this transformer-which primary is connected directly across wires 3& and 37 i in the circuit for the proceed lamp G. When transformer 42 at location B is energized by current from secondary 33 at location A, howeventhe current flowing in lamp Y from the adjacent secondary 15 is suppressed so that lamp Y is extinguished. On the other hand, when lamp Y is lighted, the adjacent relay K is energized and the thermo-sensitive element of this relay then forms .a low resistance shunt around the adjacent lamp (it so that this lamp is extinguished.

As shown in the drawing, the section to the left of location A is occupied by a car or train W, so that track relay K at location A is de-energized with the result that relays K K K and K at this location are also tieenergized. Owing to thefact that relay K is 'de-energized, the stop lamp R of signal 'S is lighted, so that this signal indicates stop. Considering signal S the proceed lamp G is: extinguished because relay K at location A is de-energized. The caution lamp Y is lighted because relay K at location B is energized and the primary of transformer-42 is de-energized, due to the fact that relay K? at location "A is'Kdeenergized; The stop lamp R is extinguished because the adjacent relay K is energized. At signal S the proceed lamp G is lighted because relay K at this signal and relayK at location B are both energized. The cantion lamp Y is extinguished because the current supplied to this lamp by the adjacent secondary 15 is neutralizedby current supplied to the adjacent transformer 42 from secondary 33 of transformer T The stop lamp R is extinguished because the adjacent relay K is energized.

I have found that of the thermo-sensitive materials suitable for use in the-rino-sensitive relays, those having negative temperature cient substances that may be readily utilized.

It follows, therefore, that for relays of this character substances having negative temperature coefiicients are preferable to substances having positive temperature coeilicients. One feature of the present invention is that all of the thermo-sensitive relays have negative temperature coefiicients.

Although I have herein shown and described only three formscf signaling apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention. I

Having thusdescribed my invention, what I claim is: 1 i

1. In combination, a plurality of successive sections of railway track. a track circuit for each section including a. source of current and the heating element of a thr-rmosensitive relay K a signal for each section comprising proceed, caution and stop lamps; a circuit for the proceed lamp of each signal including a source of current, the th-ermo sensitive element of relay K and the heating element of a thermo-sensitive relay K a branch for each proceed circuit passing around said lamp, thermo-sens-itive element, and heating element, including theheating elements of two thermo-sensitive' relays K and K; a circuit for the stop lamp of each signal including a source of current and the thermo-sensitive element of relay K a circuit for the caution lam of each signal including a source of current, the thermosensitive element of the adjacent relay K the thermo-sensitive element of relay K at the next signal in advance and. the primary or" a transformer; a thermo-sensitive relay K for each signal the heating element of which is connected with the adjacent transformer. and a shunt around each proceed lamp including the thermo-sensitive element of the adjacent relay K 2. In combination, a plurality of successive sections of railway track. a track circuit for each section including a source of current and the heating element of a thermo-sensitive relay K a signal for each section comprising proceed, caution and stop lamps; a circuit for the proceed lamp of each signal including a source of current, the thermosensitive element of relay K and the heating element of a thermo-sensitive relay K a branch for each proceed circuit passing around said lamp, thermo-s-cnsitive element and heating element and including the heating elements of two thermo-sensitive relays K and K a circuit for the stop lamp of each signal including a source of current and the thermosensitive element of relav K a circuit forthe caution lamp of each signal including a source of current, the th-ermo-sensitive element of the adjacent relay K and the thermo-sensitive element of relay IQ at the next signal in advance; and means for each signal controlled by the flow of current in the caution lamp for preventing the supply of current to the proceed lamp.

3. In combination. a stretch of railway track comprising a plurality of successive sections, signals for said sections and traincontroll-ed means for governing said Signals comprising thermo-se'nsitive relays each made up of a heater and a thermo-sensitive element and all such thermo-sensitive elements having negative temperature coefficients.

4. In combination, a stretch of railway track comprising a plurality of. successive sections. signals for said sections each adapted to indicate proceed, caution and stop, and train-controlled means for governing said sections comprising thermo-sensitive relays each made up of a heater and a thermosensitive element and all such thernio-sensitive elements having negative temperature coeflicients.

5. In combination, a stretch of railway track comprising a plurality of successive sections, signals for said sections each adapted to give at. least two indications, traincont-rolled means for governing said signals, and means for each signal including a thermo-sensitive relay controlled by the current which causes the signal to give one indication for preventing the slgnal from simultaneously giving a different indication.

6. In combination, a stretch of railway tracle comprising a plurality of successive sections, signals for said sections each having at least two devices adapted when supplied with current to give contradictory indications, and means for each signal including a thermo-sensitive relay controlled by the current supplied to one device for preventing the simultaneous supply oit current to another device in the same signal.

7. In combination, two successive sections of railway track, a. track circuit for each section including a source of current and the heating element of a thermo-sensitive' relay having a negative temperature coeflicient, a signal for the rear section including a device adapted whenenergized to cause the signal 4 to indicate proceed, and means controlled by the thermo-sensitive elements of said thermoscnsitive relays and eflfective only when both of said sections are unoccupied for causing said device to be energized.

S.-In combination, two successive sections of railway track, a track circuit for each sect-ion including a source of current and the heating element of a thermo-sensitive relay having a negative temperature coefficient, a signal for the rear section including a lamp adapted when energized to indicate proceed,

and means controlled by the thermo-sensitivc elements of said thermo-sensitive relays and etlective only when both of said sections are unoccupied for causing said lamp to be energized.

9. In combination, two successive sections of railway track, a thermo-sensitive relay for each section, train controlled means for said sections for causing the relay for the rear section to be conductive only when its section is unoccupied and the relay for the forward section to be conductive only when its section is-occupied, and a signal for the rear section controlled by said relays and adapted to indicate caution when both of said re- 'lays are conductive.

10. In combination, two successive sections of railway track, a thermosensitive relay for each section, train controlled means for said sections for energizing one relay when its section is unoccupied and the other relay when its section is occupied, and a signal controlled by said relays and adapted to indicate caution when both relays are energized.

11. In combination, two successive sections of railway track, a thermo-sensitive relay for each section, train controlled means for said sections "for energizing the relay for the rear section when its section is unoccupied and the relay for the forward section when its section isoccupied, and a signal controlled by .said relays; and in dicating caution when both relaysare energized. f 4 1 .12. f In combination,.,.a track circuit com prising. track rail's', a I source] of current and jai heatingunitg a secondcircuit ncludlng an element exposed to heat from said iiinit and having the characteristics of varying in electiical resistancelwith changes of temperature, and asignal com ouedgby said second circuit.

13,; In combi nation, an element having the characteristic of varying in electrical resistance in response to changes of temperature, an electrical heatingunit associated with said element, train controlled means for varyingthe current supplied to said heating unit, and a railway traific governing device responsive .to changes in the resistance of said element due to changes in the heating current supplied to said unit and arranged to give one indication in response to a steady resistance of one value and a different indication in response to a steady resistance of a di-fi'erent value.

14. In combination with the rails of a railway track, a source of current and a heating unit connected therewith, a circuit independent of said track rail circuit and in:

cluding 'an element having a negative temperature coeflicient exposed to heat from-said unit, and a signal controlled by said circuit.

15. In combination with the rails of a railway track, a source of current and a heating unit connected therewith, an element having a negative temperature coefli-' cient exposed to heat from said unit, and

a circuit independent of said track rail circuit and including said element for controlling a signal lamp.

16. In combination, a railway track, a heating unit, train-controlled means for supplying current tosaid unit, an element exposed to heat from said unit and having the characteristic of varying in electrical resistance with changes in temperature, a circuit independent of said traincontrolled means and including said element,"and a signal controlled, by said circuit.

17. In combination, a railway track, a heating unit, train-controlled means Ior supplying current to said unit, an element having a negative temperature coefficient eX- p'osedto heat from said unit, a circuit distinct from said traincont-rolled means and including said element, and a. signal controlled by said circuit.

18.-In combination, a track circuit comprising track rails, a source of current and a heating unit; an element exposed to heat from said unit and having the characteristic of varying in electrical resistance with changes of temperature, and a railway traffic governmgdevice responsive to changes Ian the resistance of said element due to changes in the heating current supplied to said unit and arranged to give one indicat on Xres'ponse to a steady resistance otone value fandja "different indication in response to a steady resistance ofa difierentjvalue.

l9. combination, an element having a negative temperature coefficient, an electrical'lieating unit associatedwith said element,

train-controlled means for 'varyin'gthe 'cu'rrent supplied tofsaid heating' 'unit, and a lway' tr'aflic governing device responsive to anges theresistance ofsaid element 'duetochanges in. the heating current supplied to said unit and arranged to give one indication in response to a steady resistance of one value and a different indication in response to a. steady resistance of a different value. I

20. In .combination, a section of railway track, an element having the characteristic of varying in electrical resistance in response to changes in temperature, an electrical heating unit associated with said element, means for supplying more'heating current to said heating unit when said section is unoccupied than when the section is occupied, and a traflic governing device responsiveto changes in the resistance of said element due to changes in the heating current supplied to said unit and arranged to give one indication in response to a steady resistance of one value and a different indication in response to a steady resistance of a different value.

21. Railway signaling apparatus comprising a section of track, a circuit including a heating unit, means for supplying current to said circuit when said section is unoccupied but not when it is occupied, an element exposed to heat from said unit and having the characteristic of varying in electricalresistance in response to changes in temperature, a second circuit independent of said first cir cuit and including said element. and a signal controlled by said second circuit.

22. In, combination, a section otrailway track, a track circuit for said section including a source of current and a heating unit, an element receiving heat from said unit and responsive to temperature variations by varying inresistance, a plurality of secondary heating units controlled by said element, asecondary temperature-responsive element for each secondary unit receiving heat from the unit and a signal for the section con trolled by said secondary elements.

23. In combination, a. relay comprising a thermosensitive element and a. heating unit, train-controlled means for varying'the current supplied to said heating unit, and a railway traflic controlling device controlled as to its indication by changes in the resistance of said elementdue to changes in the amount of current supplied to said heating unit. Y r

24.- In combination, a relay comprising a thermo-sensitive element and a heating uni-t, train. controlled means for varying the current supplied to said heating unit, anda railway trafiic controlling device selectively responsive to d-ifierent steady values of the a resistance of said thermo-sensitive element with said track rails and a thermo-sensitive element exposed to ,heat from said unit, and a railway traffic controlling device selectively responsive to different steady values of the resistance of said thermo-sens'itive ele- I ment as determined by different steady values of the. current supplied to said heating unit from said track rails.

In Witness whereof I afiix my signature.

. LABS O. GRONTDAHL, 

